Unlike most light, propagation-invariant beams neither diffract nor disperse when they pass through a medium, allowing them to sustain their focal width for more than the Rayleigh length and to self-heal after they encounter an obstacle. All non-diffracting beams are characterized by tight correlations between the spatial and temporal frequencies underlying their beam profiles, which is why they are often realized using pulsed lasers, as a loss of spatiotemporal coherence is expected to destroy the beams’ non-diffracting nature. But now, Murat Yessenov and co-workers have succeeded in creating non-diffracting beams with fully incoherent light, operating instead in quasi-continuous-wave mode.
Taking inspiration from ultrafast optics, Yessenov and colleagues used a fully linear approach to shape the wave from an incoherent broadband LED, imparting it with the necessary correlations to create non-diffracting beams with a 300-fold enhanced Rayleigh length. The advance could relax the source requirements for imaging thick samples with, for example, light-sheet microscopy.
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Meinzer, N. Stay in shape. Nat. Phys. 15, 522 (2019). https://doi.org/10.1038/s41567-019-0557-x